Fuze



M. J. ROGERS ETAL 3,006,280

FUZE

Oct. 31, 1961 Filed April 13, 1954 2 SheetsSheet 1 I9 I r uxl/ $45 38IGNITER DETONATOR BOOSTER EXPLOSIVE FIG. 1

MILTON J. ROGERS INVENTORS Oct. 31, 1961 M. J. ROGERS EI'AL 3,006,230

FUZE

Filed April 13, 1954 2 Sheets-Sheet 2 JEROME B. MEYER MILTON J. ROGERSINVENTORS Unitec'r states Pmerrt r r 3,006,280 FUZE Milton J. Rogers andJerome B. Meyer, Baltimore, Md.,

assignors to Aircraft Armaments, Inc., Baltimore, Md. a corporation ofMaryland Filed Apr. 13, 1954, Ser. No. 422,796 7 Claims. (Cl. 10270.2)

This invention relates generally to fuzes and more particularly to anacceleration sensitive fuze for bombs and the like, which employs aplurality of piezoelectric crystal units which will generate electricalenergy in response to pressure exerted thereon.

In general, the fuze device comprises a hollow spherical housing with aball carried therein so as to exert a force on at least one of aplurality of pressure sensitive piezoelectric crystals such as bariumtitanate ot produce electrical energy in amounts which vary directlywith the acceleration of the fuze in any direction. By employing such adevice in a bomb for effecting detonation of explosives it is notnecessary that the bomb maintain a given attitude as is necessary in thecase of bombs employing directional sensitive impact type fuzes. Thebomb may first contact the target with its nose or side or tail anddetonation will occur; the only requirement being that the bomb strikethe object with sufiicient force to impart an acceleration, positive ornegative, of sutficient magnitude to generate the required amount ofelectrical energy in the fuze for effecting detonation. Thus, even aglancing blow by the bomb on a target such as an enemy aircraft willcause the bomb to explode.

An object of this invention is to provide an acceleration sensitive fuzewhich will generate electrical energy in sufficient quantities A ithoutamplifica ente'efieet eetena tion of common explosive material and whichresponsive to accelerations applied to the fuze from any direction.

Another object of this invention is to provide an acceleration sensitivefuze which is capable of withstanding very high accelerations withoutdamage and which is small and compact by construction.

Another object of this invention is to provide an acceleration sensitivefuze which will operate under reasonably high temperature conditions,which is economical to manufacture and dependable in operation.

Still another object of this invention is to provide a fuze for bombsand the like of the type which is adapted to explode on impact, whereinthe fuze may be mounted in any location within the confines of thedevice without affecting its operation.

Further and other objects will become apparent from a reading of thefollowing description, especially when considered in combination withthe acompanying drawings, wherein like numerals refer to like parts.

In the drawing:

FIG. 1 is an exterior view of the fuze, including a typical schematiccircuit arrangement illustrating the use of the fuze in a bomb.

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1.

FIGS. 3 and 4 are sectional views showing modified forms of thepiezoelectric crystal units.

Referring to FIGS. 1 and 2, the fuze includes a hollow spherical housing1 which is made up of two hemispherical bodies 2 and 3 which are firmlysecured together by suitable means such as bolt and bracket assemblies4. A solid spherical ball 5 of material such as steel is carried withincavity 6 of housing 1. The diameter of ball Sis less than the diameterof cavity 6 by an amount which will allow sufiicient relative movementto properly load the piezoelectric crystal units 7 carried by housing 1as hereinafter described.

A total of six piezoelectric crystal units 7 are carried by housing 1and symetrically arranged relative to each r', I. I I I 1C6 PatentedOct. 31,

other on three mutually perpendicular axes. Threaded openings 8 areprovided in the housing for receiving the units 7 and securing them inthe proper position relative to ball 5. As best shown in FIG. 2 thepiezoelectric 5 crystal units comprise an outer tubular sleeve 9 whichthreadedly engages housing 1 and telescopically receives an inner sleeve10 of suitable electrical insulating material. The outer end of sleeve 9is provided with a head 11 which projects beyond the outer surface ofhousing 1 to provide means for easily installing and removing thecrystal units. An insert 12 of suitable electrical insulating materialis arranged transversely of sleeve 10 to firmly abut head 11 and providean insulated seat in the chamber for receiving a wafer 13 ofpiezoelectric crystal material such as barium titanate. A sliding washer14 of electrical insulating material is located within sleeve 10adjacent wafer 13 to completely insulate the barium titanate materialand yet allow forces to be applied thereto by ball 5 through apiston-like member 15 which is slidably received by sleeve 10. A concaveseating surface 16 is provided on the outer end of piston 15 for makingsurface to surface contact with ball 5. To avoid applying damaging shockloads on the barium titanate wafer 13, a layer 17 of sponge rubber orthe like may be inserted between piston 15 and the insulating washer 14.The electrical potential developed by wafer 13 is picked up by a pair ofelectrical leads 18 and 19 which connect with the wafer on oppositesides thereof, wherein the opposite sides are transverse to thedirection of the compressive force applied by piston 15. Holes 20 and 21are tapped in head 11 and sleeve 9 to provide an exit for leads 18 and19 from unit 7.

As shown in FIG. 2, piezoelectric crystal units 7 project into cavity 6of housing 1 to suspend ball 5 centrally within the mity and out ofcontaet withthea'nner of housing 1.

The modified piezoelectric crystal unit 22 as shown in FIG. 3 is similarto unit 7 described above in connection with FIG. 2 except that piston15 and sponge rubber insert 17 of unit 7 are replaced by a mechanicalspring 23 and piston 24 assembly wherein piston 24 engages theinsulating washer 14 directly and spring 23 projects into cavity'6 toengage ball 5. This arrangement shown in FIG. 3 will more eflicientlyabsorb shock loads without danger of damaging the barium titanate wafer13, but will allow greater freedom of movement of ball 5 within thecavity and therefore would be less desirable in applications where thefuze is subjected to vibrations of large amplitude.

A second modification of the piezoelectric crystal unit is shown in FIG.4, wherein the openings 25 in housing 1 are tapered inwardly so that thebarium titanate piezoelectric crystal material 26 may be wedged into asecure position for engaging ball 5 directly rather than through apiston and insulator as shown in FIGS. 2 and 3. As seen in FIG. 4, thebarium titanate material 26 is electrically insulated from housing 1through the use of sleeve 27 and insert 28. The barium titanate material26, as well as the insulation 27 and 28, are secured in positionrelative to housing 1 by use of a cover plate 29 which is secured to thehousing by suitable means such as screws 30. Since in the arrangement ofFIG. 4, ball 5 contacts the piezoelectric crystal material 26 directly,the energy generated may be picked up by measuring the voltage potentialbetween ball 5 and the outer surface of the barium titanate material 26.This may be done very simply by tapping a hole 31 in housing 1 andinserting a spring urged contact element 32 therein which contact ball 5at all times, even though the ball may move relative to the housing. Anoutput lead 33 firmly attached to contact member 32 is fed through anopening 34 in'housing 1. The lead 35 is firmly attached to the outersurface of the barium titanate material 26 and fed through a smallopening 36 in cover plate 29. By conhousing 1. This arrangement, whilebeing very simple in construction, has certain disadvantages over theconfiguration shown in FIG. 2 in that any oxidation on the surface ofball 5 or on pick-up element 32 will decrease the'output energyobtainable from the piezoelectric material 26. Also forming thepiezoelectric material itself to the curved shape of ball 5 so thatsurface to surface contact may be obtained is quite difiicult andexpensive to accomplish as compared with making flat wafers 13 as usedin the forms shown in FIGS. 2 and 3. a

The operation of the fuze is believed obvious from a reading of theforegoing description. A force applied to any one of the piezoelectriccrystal units will cause the latter to generate electrical energy inquantities varying directly with the magnitude of the force. Due to thepull of gravity, the fuze will produce a small output voltage eventhough it is not being. occelerated. However, this small output due togravity is negligible when using the fuze for igniting the explosive inbombs and the like, since the accelerations imparted to the bomb, evenwhen it strikes the target with only a glancing blow, will bemany timesthe 1 g loading due to gravity and hence a sufiicient diflference in theenergy output of the fuze will be obtained to eifect detonation.

A typical circuit for use of the fuze in a bomb is shown in FIG; 1,wherein output leads 19 are fed to ground and output leads 18 connectingwith the positive sides of the piezoelectric wafers are all connected toan arming switch 37 which, when closed, will allow the electrical energygenerated by the fuze to be applied to an igniter 38 through lead 39.The agniter 38 in response to an electrical impulse of sufiicientmagnitude from the fuze Will eiiect detonation of the bomb explosive 40through conventional powder stages such as those identified in FIG. 1 asdetonator 41 and booster 42.

Arming switch 37 is employed to prevent electrical communication betweenthe fuze and igniter 38 while the bomb is being handled. This switch maybe operated by any suitable device such as a mechanical actuator 43which is responsive to releasing the bomb for closing the switch andcompleting a circuit from the fuze to igniter 38.

The efliciency of piezoelectric material such as barium titanatedecreases with increasing temperatures and since in certain applicationsthe fuze may be subjected to a considerable amount of heat such as thatgenerated by skin friction on high velocity rockets and projectiles, itmay be desirable to construct outer tube 9 and head 11 of thepiezoelectric crystal units 7 from a ceramic type of material whichpossesses good heat insulating properties. If further insulation fromheat should become necessary housing 1 could also be made from heatinsulating materials.

The fuze described herein may be used not only to efiect detonation ofexplosives, but also to provide guidance information for controlling themovement of a body. That is, by measuring the difference in the outputsof the various piezoelectric crystal units 7 in the fuze, the change inmovement of a body and the direction of that change may be determined.

It is to be understood that certain alterations, modifications andsubstitutions may be made to the instant disclosure without departingfrom the spirit and scope of this invention as defined by the appendedclaims.

We claim: 7

1. An acceleration sensitive fuze for generating electrical energycomprising, a housing having a generally spherically shaped cavity, aspherically shaped mass carried within said cavity, said mass having adiameter less than the diameter of said cavity, said housing having aplurality of openings formed therein in communication with said cavity,piezoelectric crystalunits carried by said housing within said openingsand projecting into said cavity and engaging said mass to suspend thesame within the cavity and out of contact with the housing wall, saidcrystal units being responsive to the forces exerted thereon by saidmass due to accelerations in any direction for generating electricalenergy, and means electrically con- .necting with said crystal units andcompleting an external circuit conducting electrical energy generatedfrom within saidfuze.

2. An acceleration sensitive fuze for devices such as bombs and the likerequiring an electrical impulse for actuation comprising, a housingforming a container, a

mass carried within said container, said mass being smaller than theinside dimensions of said container, at least four piezoelectric crystalunits carried by said housing and engaging said mass to suspend the samewithin the container and out of contact with said housing, said crystalunits being spaced so that the points of engagement with said mass ofany three of said units be in one hemisphere of the imaginary spherewhose surface includes said points.

of engagement and the point of engagement with said mass of a fourthunit, and the point of engagement of said fourth unit lies in the otherhemisphere of said sphere at a point not diametrically opposite to anyone of the first said points of engagement, said crystal units eachbeing responsive to forces exerted thereon by the acceleration of saidmass in any direction for generating electrical energy, and meanselectrically connecting with said crystal units for conducting saidenergy exteriorly of said fuze and eiiecting actuation of the device.

3. An acceleration sensitive fuze for bombs and the like requiring anelectrical impulse for detonating the same comprising, a housing forminga container, a mass carried within said container, said mass beingsmaller than the inside dimensions of saidcontainer, a plurality ofpiezoelectric crystal units carried by said housing and engaging saidmass to suspend'the latter within the container and out of contact withthe housing, each said unit including a tubular electrical insulator, abarium titanate wafer carried within said tubular insulator, a pistonslidably received within said tubular insulator and responsive toaccelerations of said mass for squeezing said wafer and generatingelectrical energy at a voltage varying directly with the squeezing forceapplied thereto, resilient means interposed between said mass and saidwafer for reducing shock loads, and means electrically connecting withsaid wafers for conducting said energy exteriorly of said fuze andeffecting detonation of said bomb.

4. An acceleration sensitive fuze for generating electrical energy, thevoltage of which varies directly with the acceleration of said fuzecomprising, an outer housing forming a container, a mass carried Withinsaid container, said mass being smaller than the inside dimensions ofsaid container, said housing having a plurality of openings formedtherein, insulating means lining each said opening and forming a chambercommunicating with the interior of said container, piezoelectricmaterial carried within each said chamber and arranged to generateelectrical energy in response to pressure applied thereto, and pistonmeans slidably received within each said chamber and projecting intosaid container for engaging said mass and applying pressure to saidpiezoelectrical material in response to accelerations of said housing.

5. An acceleration sensitive fuze for generating elec trical energy, thevoltage of which varies directly with the acceleration of said fuzecomprising, an outer housing forming a container, a mass carried withinsaid con tainer, said mass being smaller in size than the insidedimensions of said container, said housing having a plurality ofopenings formed therein, insulating means lining each said opening andforming a chamber communicating with the interior of said container,piezoelectric material carried within each said chamber and evilarranged to generate electrical energy in response to pressure appliedthereto, shock absorbing piston means slidably received within each saidchamber and projecting into said container for engaging said mass andapplying pressure to said piezoelectric material in response toaccelerations of said housing causing said mass to press against saidpiston means, and means electrically connecting with said piezoelectricmaterial for conducting said electrical energy in a circuit exteriorlyof said fuze.

6. An acceleration sensitive fuze for generating electrical energy, thevoltage of which varies directly with the acceleration of said fuzecomprising, a container, a mass of electrical conducting materialcarried within said container, said mass being smaller than the insidedimensions of said container, said container having a plurality ofopenings formed therein, insulating means lining each said opening andforming a chamber communicating with the interior of said container, ablock of piezoelectric material secured'Witlain each aaid thamber andprojecr ing into said container and engaging said mass to support thelatter in a position out of contact with said housing, saidpiezoelectric material being responsive to pressure exerted by said massfor generating electrical energy, an electrical contact element carriedby said container and engaging said mass to provide a common ground forall the blocks of piezoelectric material, and means connecting with eachsaid block of piezoelectric material for completing an external circuitconducting electrical energy generated from within said fuze,

7. A fuze for eifecting detonation of explosives com- 30 andwiring'rneans eleetrieaiiy eormeeting wirh 'said 'piezo prising, ahollow spherical container, a ball carried within said container, saidball being smaller in diameter than the inside diameter of said hollowcontainer, said container having a plurality of openings formed therein,a piezoelectric crystal unit carried by said container within each saidopening, each said unit comprising an electrical insulating tubularmember forming a chamber communicating with the inside of said hollowcontainer, a water of piezoelectric material carried within each saidchamber for generating electrical energy in response to pressure appliedthereto, a piston assembly slidably received within each said chamberadjacent said water and projecting into said container for engaging saidball to support the latter in a position out of contact with thecontainer Wall, each said piston assembly being responsive to inertiaforces applied by said ball for applying pressure to said water, saidassembly including cushioning means for absorbing shock loads applied bysaid ball,

electric material for conducting said electrical energy to theexplosives for efiecting detonation.

References Cited in the file of this patent UNITED STATES PATENTS2,488,586 Diemer NOV. 22, 1949 2,514,297 Smith et al. July 4, 1950FOREIGN PATENTS 277,052 Switzerland Nov. 1, 1951

